Ge-se-te glass and infrared detection system



Ge-$e-Ta GLASS AND INFRARED DETECTION SYSTEM Filed-April 22, 1965 Oct. 17, 1967 M. J. BRAU ETAL 2 Sheets-Sheet 1 INVENTORY, Maurice J. Brau Rowland E. Johnson Robert J. Puffer-son I O 3: .82 22 8 $2 3: R: 32 go? 20:69.28 $30 S01E22 M53535 4 Oct. 17, .1967 M. J. BRAU ETAL 3,348,045

Ge-Se-Te GLASS AND INFRARED DETECTION SYSTEM Filed April 22, 1965 2 Sheets-Sheet 2 CURVE I.

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INFRARED RAY INVENTORS. Maurice J. Brau Rowland E. Johnson Robert J. Patterson BY 13W ATT'Y United States Patent ,3 r l c Ge-Se-Te GLASS AND INFRARED DETECTION SYSTEM Maurice J. Bran, Richardson, and Rowland E. Johnson and Robert .1. Patterson, Dallas, Tex., assignors to Texas Instruments Incorporated, Dallas, Tex., a corporation of Delaware Filed Apr. 22, 1965, Ser. No. 450,125 2 Claims. (Cl. 250-83) ABSTRACT OF THE DISCLOSURE Disclosed are compositions of matter comprising germanium, selenium, and tellurium, many samples of which have been found to be glasses transmitting in the infrared region of the electromagnetic spectrum, and some of which have been found to be crystalline. Also disclosed are methods of compounding these compositions, and an illustration of the use of the glass compositions of this invention as a transmitting element within an infrared detection system.

This invention relates to amorphous compositions of matter. More particularly it relates to infrared transparent glasses.

The invention disclosed herein appertains to germanium-selenin-m-tellurium amorphous glass compositions which are transparent to the infrared region of the electromagnetic spectrum. Moreover, the invention provides amorphous glass compositions having good transmission in the one to 20 micron wave length region of the electromagnetic spectrum.

The glass of the invention may contain about 5 to 38 atomic percent germanium, 18 to 85 atomic percent selenium, and 0 to 62 atomic percent tellurium, and may be made by reacting the constituents to form a melt and quench-cooking the melt from about 800 C. to 900 C. to room temperature in air.

It is therefore an object of the invention to provide an amorphous glass composition comprising in major proportion, or consisting essentially of, germanium, selenium, and tellurium.

Another object of the invention is to provide an amorphous glass composition having a high transmission in the one to 20 micron wave length region of the electromagnetic spectrum.

A further object of the invention is to provide a ternary amorphous glass composition comprising in major proportion or consisting essentially of from 5 to 38 atomic percent germanium, 18 to 85 atomic percent selenium, and from greater than 0 to 62 atomic percent tellurium.

Another object of this invention is to provide a ternary germanium-selenium-tellurium amorphous glass composition having good transmission at high temperatures in the one to 20 micron wave length region of the electromagnetic spectrum.

Still another object of the invention is to provide a ternary gerrnanium-selenium-tellurium amorphous glass composition exhibiting a high softening point and good transmission in the one to 20 micron region of the electromagnetic spectrum.

These and other objects, advantages and features of the invention will become more readily apparent from the following detailed description when read in conjunction with the appended claims and attached drawings wherein:

FIGURE 1 depicts a ternary diagram of the atomic percentages of germanuim, selenium, and tellurium for various amorphous compositions of matter of the invention;

FIGURE 2 is a graphical representation of percent transmission at room temperature at various wave lengths of the electromagnetic spectrum for various glass compositions according to this invention; and

3,348,045 Patented Oct. 17, 1967 FIGURE 3 illustrates one particular form of the glass compositions of this invention, usable as an infrared transmitting element, such as a dome or lens, within an infrared detection system.

Referring to FIGURE 1, various compositions of germanium, selenium, and tellurium were compounded and evaluated to determine whether they were amorphous or crystalline. The general procedure for making the various compositions is described hereinafter.

Various atomic percentages of germanium, selenium, and tellurium were chosen for each sample to be made. The appropriate amounts of the constituent were weighed and then placed in a previously cleaned quartz ampoule. An example of a suitable cleaning step for the ampoule is brushing in a suitable detergent solution, rinsing thoroughly in deionized water, and then drying. The total weight of each of the samples was between five and 15 grams. The constituents were placed in the cleaned tube, evacuated to about 10* torr, and sealed. The sealed tube was then placed in a furnace and gradually heated to a temperature of about 800 C. to 900 C. and held at that temperature for about 16 hours to provide sufficient time for the constituents to react completely with each other. The furnace was a rocking furnace which may be of any suitable design to provide agitation of the constituents so as to achieve complete reaction thereof. The samples were then removed from the furnace and held in a vertical position in air for air quenching and allowed to cool to room temperature. Care was taken throughout the process to prevent heating the constituents in air to avoid causing any oxide formation. In particular, in some cases the inside surface of the ampoule was carbon coated for the purpose of chemically reducing any extraneous oxides present.

The sample compositions which failed to form amorhous glass by the air quench-cooling technique and were crystalline after quenching are presented in Table I below, whereas the compositions which formed amorphous glass are presented in Table 11 below, with the softening point results obtained for the glass. The softening point is defined as the temperature at which a pointed quartz rod under a 70 gram load penetrates a smooth surface to a depth of 0.05 mm. where the rod is in perpendicular alignment with respect to the sample, and the oint defines a 90 included angle. The reaction conditions for the samples in Tables I and II below were the same:

TABLE I Composition, Atomic Percent SampleNo. H

Ge Se Te TABLE II v 7 Composition, Atomic Percent Sample No Softening Point in 0. Ge Se Te 7 T'Approximatel value.

In FIGURE 1, the peripheral line A generally circumscribes the amorphous compositions of germanium selef nium, and tellurium according to the invention. The sam- 'ples which failed to form amorphous glass by the air quench-cooling'technique (listed in Table I) are plotted V 'on FIGURE 1 by block triangles and identified by sample numbers. The sample compositions forming amorphous glass (listed in Table II) are also plotted in FIGURE 1 within the area generally circumscribed by line A and designated by black dots, each dot being identified, by a sample number. r

In FIGURE 2, the percent transmission of radiation of the electromagnetic spectrum at room temperature in the a one to 20 micron wave length region is plotted for .various served, as shown by curve 1, due in large part to the 7 presence of extraneous oxides in these represented compositions. This absorption band was substantially eliminated, how'ever, when the ampoule which the samples were prepared had its inside surface initially carbon coated in order to reduce these oxides. The resulting curve, after elimination of the absorption band, is represented by curve 2. i i a 7 FIGURE 3 depicts a form of the glass compositions of this invention usable within a particular infrared detecting'system.-:The' detecting system is normally composed of a detector 1 having a responsive elementsensitive to infrared energy striking its surface, and an infrared transmitting element 2 such asa domeor. lens inoptical conthe compositions have relatively high indexes 'of refrac-I tion, ranging from approximately 2.3 to 3.0 at 3-5 1. wave length. Consequently, when infrared rays strike the dome 2 at the incident angle 5, as pictured in FIGURE 3, the

5 high index of refraction of the dome material causes'the tact with the detector. The optical properties of'the 7' amorphous glass compositions of this'invention make them particularly suited, among other applications, for use as' rays to be bent toward the-detector unit 1 'at'the angle-of V refraction 5, thus increasing the efliciency of detection.

The amorphous glass composition of this invention offer substantial advantages for the fabrication of the trans mitting elements for a variety ofother reasons. First, there is a wide range of physical, properties from which the designer may choose. For example, the softening points range from approximately 132 C. to 398 C., and

the Knoop hardnesses of the compositions have been measured from to as high as 153. Second, these compositions offer substantial advantages over crystalline 7 material in that they maybe'heated to a plastic state and.

easily worked into desired shapes and sizes. Third, the reasonably high softening points and available hardnesses offer greater ease in grinding, polishing, and handling operations, as well as stability to thermal shocks.

It should be understood that although most of the samples discussed above were essentially germanium, selenium, and tellurium, minor percentages of silicon, sulfur, phosphorus, antimony, arsenic, bismuth, etc. may be used in the glass of the invention to provide variations in the softening point and wave length transmission. I

Although only the air quench-cooling method has been described for making the amorphous compositions of,

matter, other methods could be used; Itlis also to be appreciated that many other variations and changesinf' 'the invention will suggest themselves to thoseskilled -in the'art, and such variations and changes are deemed to" 'be within the purview and scope of the invention as defined in the appended claims.

What is claimed is:

1. Ternary glass compositions consisting essentially of f germanium, selenium and tellurium and lying within Line .A of FIGURE 1. V f v v 2. An infrared detection system comprising a detector" sensitive to infrared energy and a transmitting element in optical contact with said detector, said transmitting ele- V ment comprising a ternary glass composition consisting essentially of germanium, selenium and tellurium and lying within Line A in FIGURE 1.

References Cited UNITED STATES PATENTS 3,261,721 7/1966 Cornish 23 315 x) 1 OTHER REFERENCES Borisova et aL, Zhurnal Prikladnoi'Khimii, vol. 35,;

No. 4, pp. 774 7, April 1962.

Borisova et al.', Kinetics of Dissolution of the Glassy Germanium-Selenium System in Alkaline Solutions, 1.

Applied Chemistry, vol; 36 (1963) (Translated from Zhurnal'PrikladnohKhirnii; vol. 36 No; 2, pp. 233-236,

February 1963) (pp. 221-224). V i Borisova et al;, On Electrical Conductivity of Crystal lizing Glasses GeSe As (XLOLS) Bull. Leningrad University No. 22 1962) auth. for'publ. 11-29-62 and HEL NM. MCCARTHY, Primary Examiner. 

2. AN INFRARED DETECTION SYSTEM COMPRISING A DETECTOR SENSITIVE TO INFRARED ENERGY AND A TRANSMITTING ELEMENT IN OPTICAL CONTACT WITH SAID DETECTOR, SAID TRANSMITTING ELEMENT COMPRISING A TERNARY GLASS COMPOSITION CONSISTING ESSENTIALLY OF GERMANIUM, SELENIUM AND TELLURIUM AND LYING WITHIN LINE A IN FIGURE
 1. 